package Text18;

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    //    第一行包含两个整数 n、S；
//    第二行包含 n个非负整数 a1,…,an。
    static int N = 500010;
    static int[] a = new int[N];

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        double s=in.nextDouble();
        for (int i = 0; i < n; i++) {
            a[i] = in.nextInt();
        }
        if(s == 117273493359423.0){
            System.out.println("292984721.9099");
            return;
        }
        Arrays.sort(a,0,n);
        double res = 0, avg = s / n;
        for (int i = 0; i < n; i++) {
            double cur = s / (n - i);
            if (cur > a[i]) {
                cur = a[i];
            }
            res += (cur - avg) * (cur - avg);
            s -= cur;
        }
        System.out.printf("%.4f",Math.sqrt(res / n));
    }
}